In many areas, salt water and fresh water are separated by various types of barriers, such as water divider walls and land barriers. These barriers are often needed to separate fresh from salt water due to the various types of organisms, plants, and animals that can survive only in one type of environment, i.e., either in salt or in fresh water, but not both. Another purpose for these barriers is to separate a fresh water body from a salt water ocean, so as to protect the fresh water body from ocean tides, waves and currents. These barriers are especially necessary in cases where boats and other watercraft are stationed in the fresh water body. In some cases, a governmental authority may require such a barrier between fresh water bodies for environmental reasons. The aforementioned barriers, however, can pose an obstacle to boats and other watercraft that frequently require access between the two bodies of water.
The term “portage” refers to carrying a boat and/or its supplies overland from a first body of water, between two waterways or around an obstacle to navigation. Applicant's U.S. Pat. Nos. 6,457,904, 6,174,106, and 5,947,639 provide approaches to the problem of transferring boats over barriers, from one body of water to another. A lasting problem with such portage devices, however, involves the mechanism for lifting and lowering the boat in the vertical direction.
As seen in Applicant's aforementioned patents, the mechanism for lifting and lowering the boat in a vertical direction can involve the use of at least one or two vertically-positioned cables that are coupled to the lifting apparatus on the top end and coupled to the boat at the bottom ends. Upon activation of the lifting apparatus, a drum at the top end of the cable begins to spin, thereby gathering the length of the cables upon its cylindrical exterior surface and lifting the boat in a vertical direction. Although effective for lifting, this structure requires lengthy amounts of cable, numerous moving parts, an electrical-powered drum device that requires substantial amounts of current to operate and considerable maintenance. Furthermore, ball bearings, which are used in a drum-cable implementation described above, can be expensive, thereby increasing construction costs. Lastly, the motor and brakes needed in the drum-cable implementation require periodic maintenance, thereby increasing operating costs.
Therefore, a need exists to overcome the problems with the prior art as discussed above, and particularly for a more efficient way to portage a boat from one body of water to another.